Direct VM

Since Camel 2.10

Both producer and consumer are supported

The Direct-Vm component provides direct, synchronous invocation of any consumers in the JVM when a producer sends a message exchange.
This endpoint can be used to connect existing routes in the same camel context, as well from other camel contexts in the same JVM.

This component differs from the Direct component in that Direct-VM supports communication across CamelContext instances - so you can use this mechanism to communicate across web applications (provided that camel-core.jar is on the system/boot classpath).

At runtime you can swap in new consumers, by stopping the existing consumer(s) and start new consumers.
But at any given time there can be at most only one active consumer for a given endpoint.

This component allows also to connect routes deployed in different OSGI Bundles as you can see here after. Even if they are running in different bundles, the camel routes will use
the same thread. That autorises to develop applications using Transactions - Tx.

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URI format

direct-vm:someName

Where someName can be any string to uniquely identify the endpoint

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints.

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

The following two sections lists all the options, firstly for the component followed by the endpoint.

Component Options

The Direct VM component supports 7 options, which are listed below.

Name Description Default Type

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

boolean

block (producer)

If sending a message to a direct endpoint which has no active consumer, then we can tell the producer to block and wait for the consumer to become active.

boolean

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

boolean

timeout (producer)

The timeout value to use if block is enabled.

long

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

boolean

headerFilterStrategy (advanced)

Sets a HeaderFilterStrategy that will only be applied on producer endpoints (on both directions: request and response). Default value: none.

HeaderFilterStrategy

propagateProperties (advanced)

Whether to propagate or not properties from the producer side to the consumer side, and vice versa. Default value: true.

boolean

Endpoint Options

The Direct VM endpoint is configured using URI syntax:

direct-vm:name

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

name (common)

Required Name of direct-vm endpoint.

String

Query Parameters (9 parameters)

Name Description Default Type

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

  • InOptionalOut

ExchangePattern

block (producer)

If sending a message to a direct endpoint which has no active consumer, then we can tell the producer to block and wait for the consumer to become active.

boolean

failIfNoConsumers (producer)

Whether the producer should fail by throwing an exception, when sending to a Direct-VM endpoint with no active consumers.

boolean

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

boolean

timeout (producer)

The timeout value to use if block is enabled.

long

headerFilterStrategy (producer (advanced))

Sets a HeaderFilterStrategy that will only be applied on producer endpoints (on both directions: request and response). Default value: none.

HeaderFilterStrategy

propagateProperties (advanced)

Whether to propagate or not properties from the producer side to the consumer side, and vice versa. Default value: true.

boolean

Samples

In the route below we use the direct component to link the two routes together:

from("activemq:queue:order.in")
    .to("bean:orderServer?method=validate")
    .to("direct-vm:processOrder");

And now in another CamelContext, such as another OSGi bundle

from("direct-vm:processOrder")
    .to("bean:orderService?method=process")
    .to("activemq:queue:order.out");

And the sample using XML DSL:

<route>
 <from uri="activemq:queue:order.in"/>
 <to uri="bean:orderService?method=validate"/>
 <to uri="direct-vm:processOrder"/>
</route>

<route>
 <from uri="direct-vm:processOrder"/>
 <to uri="bean:orderService?method=process"/>
 <to uri="activemq:queue:order.out"/>
</route>

Spring Boot Auto-Configuration

When using direct-vm with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-directvm-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 8 options, which are listed below.

Name Description Default Type

camel.component.direct-vm.autowired-enabled

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

Boolean

camel.component.direct-vm.block

If sending a message to a direct endpoint which has no active consumer, then we can tell the producer to block and wait for the consumer to become active.

true

Boolean

camel.component.direct-vm.bridge-error-handler

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

Boolean

camel.component.direct-vm.enabled

Whether to enable auto configuration of the direct-vm component. This is enabled by default.

Boolean

camel.component.direct-vm.header-filter-strategy

Sets a HeaderFilterStrategy that will only be applied on producer endpoints (on both directions: request and response). Default value: none. The option is a org.apache.camel.spi.HeaderFilterStrategy type.

HeaderFilterStrategy

camel.component.direct-vm.lazy-start-producer

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

Boolean

camel.component.direct-vm.propagate-properties

Whether to propagate or not properties from the producer side to the consumer side, and vice versa. Default value: true.

true

Boolean

camel.component.direct-vm.timeout

The timeout value to use if block is enabled.

30000

Long